Fifteen people were killed outright and 24 injured, several critically, when two minibuses collided in western Kenya, police said Tuesday.

The accident happened around 8:30 pm (1730 GMT) Monday in the town of Webuye.

"It involved two matatus which collided head on. Fifteen people were killed on the spot," western province police chief Francis Munyambu said.

Nine of the injured were in critical condition with head injuries, while the other 15 were stable, although still seriously injured, he added.

Matatus are the local term for minibuses, a popular form of public transport, which are notoriously overcrowded, resulting in high fatalities when there is an accident.

Munyambu said the driver of one of the matatus swerved into the path of the other after colliding with a stationary tractor. He said the tractor driver, who had stopped without signalling, was blamed for causing the accident and would be prosecuted.

Road accidents are common in Kenya, where roads are poor and drivers often flout the highway code.